build

        fn build(weights: *[256]u4, symbol_count: usize) error{MalformedHuffmanTree}!HuffmanTree {
            var weight_power_sum_big: u32 = 0;
            for (weights[0 .. symbol_count - 1]) |value| {
                weight_power_sum_big += (@as(u16, 1) << value) >> 1;
            }
            if (weight_power_sum_big >= 1 << 11) return error.MalformedHuffmanTree;
            const weight_power_sum = @as(u16, @intCast(weight_power_sum_big));

            // advance to next power of two (even if weight_power_sum is a power of 2)
            // TODO: is it valid to have weight_power_sum == 0?
            const max_number_of_bits = if (weight_power_sum == 0) 1 else std.math.log2_int(u16, weight_power_sum) + 1;
            const next_power_of_two = @as(u16, 1) << max_number_of_bits;
            weights[symbol_count - 1] = std.math.log2_int(u16, next_power_of_two - weight_power_sum) + 1;

            var weight_sorted_prefixed_symbols: [256]PrefixedSymbol = undefined;
            const prefixed_symbol_count = assignSymbols(weight_sorted_prefixed_symbols[0..symbol_count], weights.*);
            const tree: HuffmanTree = .{
                .max_bit_count = max_number_of_bits,
                .symbol_count_minus_one = @as(u8, @intCast(prefixed_symbol_count - 1)),
                .nodes = weight_sorted_prefixed_symbols,
            };
            return tree;
        }